Cleaning White Film Off Fish Tank Hood

I just read to use not iodized salt and rinse well to get rid of lime in a fish tank.

I agree with the vinegar. Usually the white film is lime scale from the water.

Use full strength white vinegar. Apply and let sit for a minute or two to work at the gunk. Then rinse.

Try soaking it in vinegar. Or laying a rag soaked in vinegar on it. Will take a few hours but it works for us.
Good luck.